Chocolate-and-Cream Layer Cake

Leave room for dessert — this is one you won't want to miss. It certainly has its advantages: it's made with wholemeal flour, sprinkled with fresh fruit, and contains 6 grams of fiber per serving. But what really makes this cake so spectacular is how good it tastes.
Preheat the oven to 350°F.Prepare the cake: Brush 2 (9-inch) round cake pans with cooking spray; line the bottom of the pans with parchment paper. Brush the paper with cooking spray; set aside.Spoon the flour into dry measuring cups; flatten with a knife. In a large bowl, combine the flour, cocoa, baking powder, salt, and baking soda; beat until smooth.Put the granulated sugar, butter, and eggs in a large bowl; beat with a hand mixer on medium speed until smooth, about 2 minutes. Whisk together the buttermilk, 1/3 cup warm water and vanilla. Add the flour mixture; beat on low speed until smooth. Increase the speed to medium and beat for 1 minute.Spread the dough evenly over the prepared pans. Bake at 350 ° F until a wooden stick inserted in the center comes out clean, 23 to 25 minutes. Cool the cakes in the tins on a wire rack for 10 minutes. Turn the cakes onto a wire rack; remove the parchment paper. Let the cakes cool completely.Prepare the icing: Combine the powdered sugar, cocoa, chocolate chips, milk, butter, and salt in a small saucepan. Cook over low heat, stirring constantly, until the butter and chocolate have melted, about 3 minutes. Allow to cool slightly.Prepare the yogurt cream: Place the cream and powdered sugar in a large bowl; beat with a hand mixer on high speed until stiff peaks form, about 1 minute and 30 seconds. Add the yogurt and vanilla; beat on high speed until smooth.Place 1 cake on a cake stand or plate; brush evenly with yogurt cream, leaving a 1/2-inch thick rim. Top with the second cake. Carefully pour the chocolate icing over the top of the cake, spreading it around the edges. Top with berries and, if using, nuts.